Process for reducing objectionable odor of phosphorodithioate compounds



United States Patent PROCESS non REDUCING OBJECTIONABLE ODOR F P S O T QA E OMP UND Simon Frank, Stamford, and George N. Gagliardi, Springdale, Conn., assignors to American Cyanannd Company, New York, N.Y., a corporation of Mame No Drawing. Filed June 16, 1959, Ser. No. 820,591

7 Claims. (Cl. 260-461) This invention relates to a process for reducing the objectionable odor of a malodorous phosphorodithioate compound. More particularly, it relates to a process for the removal of odor from a malodorous phosphoro- Patented Apr. 18, 1961' ice cedure develops a strong obnoxious odor after storagefor several months. To the present, there is lacking a simple, inexpensive and expeditious process for removing the objectionable odor found in phosphorodithioate insecticides.

It has now been discovered that the objectionable odor which is characteristic of phosphorodithioate comdithioate insecticide derived from dithiophosphoric acid.

' Phosphorodithioate insecticides of the type with which the present invention is concerned are usually esters and may be represented by the general formula in which R; and R are each selected from the group consistingot aliphatic and aromatic hydrocarbon radi:

V cals, and R and 'R' are selected from the group consistin which R and R have the meaning shown above, with an unsaturated compound of the formula pncooaz asses;

in which R and R have the meaning-shown above as described in United States Letters PatentZNo'; 2,578,652.

A typical ester is O,O-dimethy1-S-( 1,2-dicarbethoxyethyl)- phosphorodithioate which is commercially availableas malathio'n insecticide.

Phosphorodithioate insecticides of the type hereinbefore described have achieved a recognized place in the art as eXtremly useful insecticides byjvir-tuevof thefact of their relatively low mammalian toxicity. Such phos-.

phorodithioate insecticides find usefor the control of asphids, spider mites, scales, house flies as well as a wide range of other sucking and chewing insects. However, more widespread use of such phosphorodithioate inwhiqh i lu he use of i u Qx dtzin suhsances.

secticides has been hampered to [a large extent because such insecticides possess an odor which is:objectionable.,, Of course, numerous expedients have been proposed in an attempt to reduce-the obnoxious odor of such com- Pounds u mmsn emp oye e hdas me or pounds, especially phosphorodithioate insecticides, can be effectively and remarkably reduced by the simple expedient of subjecting such a compound to the action of ozone. by passing an ozone containing gas through or in contact with such a phosphorodithioate insecticide, an insecticide having a pleasant ester-like odor is produced,

Such an insecticide, substantially devoid of malodor, is in contrast to both the crude or technical grade of in:

secticide and a refined grade of phosphorodithioate in secticide. Such an insecticide may be advantageouslyemployed, for example, in fly sprays and in suitable-solvents for the impregnation of textiles,.particularly arti. cles of clothing, to provide insecticidal activity. It may' be used with advantage for the control of numerous Further, the treatment renders the insecticide for even wider use, as, for ex-- ample, in grain storage elevators and the like. The in} secticide after having been subjected to the treatment. with ozone is substantially free from malodor and ac-' ceptable for use by the householder, gardener and others who have disapproved of the heretofore available in- However,. none of the active properties applicable for the destructionof insects have been lost by the treatment. The; treatment of' the present invention further improves the: insecticide in that even after prolonged storage under" variousconditions little or no objectionable odor is noted.

household and garden pests.

secticide because of its objectionable odor.

in the sortreated insecticide.

The present process, therefore, involves the passing of.

ozone,"or an ozone containing gas, through or in contact: with theinsecticide soas to reduce'the objectionable odor of amalodorous phosphorodithioate insecticide. It: has been found that the ozone used in the presentprocess: may be admixed with oxygen, air or other non-reactive diluent gases without affecting the efiiciency of the proc-- ess. Generally, an ozone concentration of from about 0.05 to about 3.5 weight percent in these gases is ef-- fective. It has been found that'as little as 0.1 weight percent of ozone based upon the weight, of insecticide Y ,may. be used in: the process though higher concentra-- tions are generally employed.- However, amounts ranging; up to about 3.5 weight percent or above are also I efiective,;but the use of a larger-amount is not especially desirable from a cost standpoint and-is also not usually required to produce the desired level of odo'rcontrol. Conventional and well-known gas liquid contact appa ratus, among which may be mentioned the-packed cola umn.type,' may be'usedior the" treatment'iof thefn-a. secticide with ozone since the apparatus employed-1 notthe essential feature or" this invention. "Further,eve t Surprisingly, it has been found that merely of ozone through or in contact with said insecticide, an.

inert and non-reactive gas such as air, oxygen, nitrogen or the like may be used to sweep out volatiles, such as residual ozone and the oxidation products produced .during the treatment, which have been expelled from the malodorous insecticide. The process may be carried out over a considerably Wide temperature range. When the insecticide to be deodorized is a liquid, temperatures from about 25 C. to about 90 C. may be effectively employed. Furthermore, while a liquid phosphorodithioate insecticide may be treated with ozone or an ozonecontaining gas in the absence of solvent at these process temperatures, it is also possible to efiect a reduction of objectionable'odor when a solvent for the insecticide is employed. Among the large number of solvents suitable for the phosphorodithioate insecticides may be mentioned esters, alcohols, ketones, hydrocarlions, and other suitable solvents which are non-reactive with the insecticides and with ozone.

In order to facilitate a better understanding of theinvention, the following examples are given primarily for the purpose of illustrating certain more specific details thereof. Unless otherwise stated, all parts are by weight.

EXAMPLE I In a continuously stirred pot reactor are placed 100 parts of technical grade, liquid 0,0-dimethyl-S-(l,2

dicarbethoxyethyl)-phosphorodithioate, having a considerable amount of malodor.

85 C. for a period of forty minutes until a quantity of ozone equal to approximately 0.5 percent by-weight of.

the charge of 0,0-dimethyl-S-(1,2-dicarbethoxyethyl)a phosphorodithioate has been passed therethrough. Air is then swept through the system toexpelvolatiles such as sulphur dioxide which may be present and residual ozone. The treated insecticide is found, to.possess a fragrant, pleasant odor in contrast to the normally malodorous insecticide.

EXAMPLE II Ina continuously stirred pot reactor are charged 100 parts of technical grade liquid O,O-dimethyl-S-(1,2-dicarbethoxyethyl)-phosphorodithioate having some malodor. An ozone-oxygen mixture, in which the amount j t a le and obnoxious odor customarily foundwith a the insecticide. t a

. It will bo obvious to those skilled in the art that there may be many minor method variations aud that differend kinds of equipment may be used in order to reduce the objectionable odor of malodorous phosphorodithioate compounds. However, in orderto illustrate even furtherpa manner in WhlCh'ithfi reduction. of-objectionable odorjmay, be accomplished fthre 'issumm'arized in the a An ozone air mixture is then bubbled through the insecticide maintained at about The-treated iuasserts Table Example III IV V 3 3 3 6 4 4 22. 5 22. 5 15 2. 6 2. 6 2. 9 1 1 1 p. C 50 25 Malathiou outlet temp.. C 70 45 Lo. ozone/ lb. malathlon 0. 5 0.5 0. 8 Odor characteristics of treated malathion 1 Fragrant lnofienslve.

plified in the foregoing description, it is to be understood that any such dithiophosphate ester, for example, 0,0- dimethyl S (1,2 dicarbomethoxyethyl) phosphorodithioate, 0,0 dimethyl S (1,2 dicarbo n propoxyethyl) phosphorodithioate, 0,0 dimethyl S- l,2 dicarbisopropoxyethyl) phosphorodithioate, 0,0- die'thyl S (1,2 dicarbornethoxyethyl) phosphorodithioate, 0,0 diethyl S (1,2 dicarbethoxyethyD- phosphorodithioate, 0,0 diethyl S (1,2 dicarbon propoxyethyl) phosphorodithioate, 7 0,0 diethyl- S (1,2 dicarbisopropoxyethyl) phosphorodithioate,

and others disclosed in United States Patent No. 2,578,652, may advantageously be treated by the process of the present invention.

We claim;

I l. A process for reducing the objectionable odor of a malodorous phosphorodithioate compound which comprises subjecting said compound to the action of ozone 'in an amount from about 0.1 percent to about 3.5 percent by weight of said compound.

2. A process for reducing the objectionable odor of a malodorous phosphorodithioate compound which comprises subjecting said compound to the action of a nonreactive gas containing ozone, the amount of ozone being 1 from about 0.1, percent to' about 3.5 percent by weight of said compound.

3. A process for reducing the objectionable odor of a malodorous phosphorodithioate compound representedby the'formula.

1 R20 CHzCOOR in which R and R are each selected from the group:

consisting of aliphatic and aromatic hydrocarbon radicals "to about 3.5 percent by weight of said compound.

' 0,0 dimethyl s table below operating conditions employed .in"additional examples in which .a malodorous phosphorodithioate compoundfis contacted with an ozone containing, gas in a conventional gas-liquidconta'ct device, a stainlesssteel columu packed with three-eighths inch Raschigphosphorodithioate commonly knownqasirnalathion' insecticide is treated in each of the followingexamples.

and R and R are each selected from the group consisting of hydrogen, aliphatic and aromatic v hydrocarbon radicals whichcomprisessubjecting said compound to? the'actionof ozone in. 'an amount fromxabout 0.1..percent 4. A process as'in claim 3 in which said compound is =-iri which RL-and-R areeach selectedfmm the group consisting of aliphatic and aromatic hydrocarbon radicals and R and R are each selected from the group consist- 6. process for reducing the'obje etionable ,odor' of (1,2 dicarbethoxyethyl) phospho- "reducing the objectionable odor of a malodorous phosphorodithioate compound represented a malodorous phosphorodithioate compound represented 7. A process as in claim 6 in which said compound is by the formula 0,0 dimethyl S (1,2 dicarbethoxyethyl) phospho- R O rodithioate.

l \fi r PS-(|JHOOORa 5 References Cited in the file of this patent R20 011200034 UNITED STATES PATENTS. in Which R R R and R are each selected from the 2,57 52 Cassaday 1 1951 group consisting of aliphatic and aromatic hydrocarbons 2,344, 20 Escobar July 22, 195 which comprises subjecting said compound to the action 2,379 234 Divine et 1 Man 24, 1959 of ozone in an amount from about 0.1 percent to about 10 3.5 percent by weight of said compound and subsequently OTHER REFERENCES passing an inert gas through the so-treated compound Hackhs Chemical Dictionary, third edition, 1944, the to expel volatiles therefrom. Blakiston Co., Philadelphia, Pa., page 609. 

1. A PROCESS FOR REDUCING THE OBHECTIONABLE ODOR OF A MALODOROUS PHOSPHORODITHIONATE COMPOUND WHICH COMPRISES SUBJECTING SAID COMPOUND TO THE ACTION OF OZONE IN AN AMOUNT FROM ABOUT 0.1 PERCENT TO ABOUT 3.5 PERCENT BY WEIGHT OF SAID COMPOUND. 